CH650732A5 - LEVEL CARD MADE OF THERMOPLASTIC PLASTIC WITH VISUALLY PERCEPTABLE SAFETY LABELS AND METHOD FOR THE PRODUCTION THEREOF. - Google Patents

Abstract

In order to form safety markings at a planar card made of a plastics material, which card may be used, for instance, as credit card, this card is built up from at least two parts. The inner border area between these two parts comprises a relief-like structure which is the carrier of the safety marking. In order to generate a watermark-like effect the upper part is made of a opaque plastic material and the other part is made of a transparent plastics material. When viewing through this card the areas of the opaque layer having the largest thickness appear as darker areas, whereby when viewing the same way the areas having a smaller thickness show a certain brightness. After being embossed the two parts of the thermoplastic material are joined to each other such that they cannot be separated such that no access from the outside is possible to this safety marking. Accordingly, an additional safety factor is arrived at in cards which can be used as money substrate, identification means or a license for any kind of access.

Description

The invention relates to a card made of thermoplastic material with flat surfaces and visually perceptible, internal security signs.

In recent times, printed cards made of plastic have found widespread use as credit, money substrate and identification cards which convey a service, represent a value or contain an access right. The partial information identifying the carrier and the features which assign the card to a specific organization or system are arranged on the card in the form of imprints, embossings, punchings or magnetic, laser or holographic information. It is now relatively easy to recreate the appearance of such cards. It is obvious that there is the possibility of misusing such cards, which are increasingly replacing cash transactions, without requiring too much effort. The public in particular has no way of convincing themselves of the authenticity of such a card. Therefore, e.g. from FR-A-2 176 463 cards are already known which are designed as composite cards, a paper layer being enclosed between two plastic layers. The paper layer is provided by means of a security print known from the banknotes and has a varying thickness as a security feature. Furthermore, parts of the plastic surfaces can also be provided with a print pattern. Although such cards offer increased security, they have several inadmissibilities. As a result of the combination of different materials, such as paper and plastic, experience has shown that the embossing of the finished card causes a deformation. The card is given a curvature in the embossing direction due to the tension that occurs, which impairs the automatic readability of the information mentioned at the outset, provided that it is provided on it. Furthermore, the structure of the known card offers the possibility of unwanted interventions. For example, the card can be separated along the paper layer, which enables manipulation of this paper layer, or the protective plastic layers can be removed using a solvent, so that the paper layer is then exposed. From such considerations, it is fundamentally undesirable for cards of this type to consist of a paper / plastic composite. Rather, it is desirable to create all-plastic cards that have the necessary security properties. Since such cards must have flat surfaces, however, no configuration has hitherto become known which has security features such as are known from more recent banknotes. Previous plastic cards with internal security signs, as shown, for example, in DE-A 2 659 639, are aimed at mechanically ascertainable structures which are not perceptible to the eye and likewise do not have a homogeneous structure, since they are provided with reflex zones and the like.

It is therefore the task of creating a card of the type mentioned at the outset which has security features which are visually recognizable by the public in the sense of conventional watermarks, but without the disadvantages mentioned.

This object is achieved by a card with the features mentioned in claim 1, and by means of a manufacturing method defined in claim 5.

The invention is explained in more detail below on the basis of exemplary embodiments by means of the accompanying drawings. Show it:

Figure 1 is a view of a card part according to a first embodiment, as it appears when looking through.

Fig. 2a is a schematic enlarged sectional view taken along the line II-II in Fig. 1;

FIG. 2b shows a view corresponding to FIG. 2, the individual parts being shown before they are combined;

3 shows a schematic enlarged sectional view of a variant of the embodiment according to FIG. 1;

4 shows a perspective enlarged view of a printed part with a wave-like relief structure;

5a and 5b each show a top view from different directions on a card which is assembled from parts according to FIG. 4.

Although the different types of embodiment already mentioned are shown individually below for the sake of clarity, it should be mentioned right at the beginning that these types of embodiments can advantageously be combined, as is indicated schematically in FIG. 5.

1 shows a section of a card 1 according to the invention in vertical supervision, one having to imagine a light source behind the card. There are two zones that can merge into one another,

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from the rest of the brightness image. A dark zone 4 and a light zone delimiting it. This corresponds to the appearance of the conventional watermark on paper, which is produced by the concentration of paper fibers at certain points, while fibers are peeled off at surrounding points, which creates the delimiting light zones. The different fiber concentrations lead to a different light transmission, which is the cause of the described effect. In the card according to the invention, which is not supposed to have a paper insert but is constructed entirely from thermoplastic, the aforementioned watermark cannot be produced in the manner described. Rather, as can be seen from FIGS. 2a and b, a card is constructed from two half parts 2, 3. One half part 2 is made of transparent plastic, the other half part 3 is made of opaque, i.e. translucent, cloudy plastic. Such material has an increased light absorption coefficient β, so that the light already passes through a relatively thin layer of e.g. 0.4 mm is noticeably weakened. One now takes advantage of the fact that the light absorption depends on the distance traveled, according to the law:

I = I0. e ~ Ps, where

I0: incident light intensity

I: light intensity after the distance S

ß: light absorption coefficient.

A larger layer thickness therefore leads to greater light absorption. The influence of the transparent half part 2 can be disregarded here, since its light absorption coefficient β is negligibly small in comparison with that of the opaque layer. The opaque half part 3 is now formed in such a way that regions 4 of increased thickness are formed to form a watermark-like effect. In contrast, zones 5 of smaller thickness are formed in adjacent areas 5, so that lighter areas 5 are created when looking around the dark-appearing areas, as is characteristic of the appearance of conventional watermarks. In Fig. 2b this is indicated schematically by arrows, which on the one hand represent the uniformly incident light and on the other hand the light passing through, the thickness of the arrows corresponding to the light intensity. The relief in the opaque half part 3 is embossed in such a way that the total amount of material remains constant and only a shift in the amount of material from the areas 5 to the areas 4 takes place. This means that the average thickness over the areas 4 and 5 provided with a relief structure is equal to the thickness of the rest of the map. The impression is taken with a stamping mold of a known type. The transparent half part 2 is provided with a corresponding, opposing stamping, the stamping mold used for this purpose being preferably electrolytically molded from the first stamping mold. The two half parts are then inseparably formed into a single part by laminating. Polymerization of the plastic molecules takes place along the interface of the two half-parts provided with the relief structure, so that a molecular connection is formed which makes separation impossible. It goes without saying that graphic patterns can also be printed on the inner interfaces, if this is desired. This will be discussed in more detail in connection with other exemplary embodiments. The surfaces of the card 1 thus formed are flat and can be printed or coated in a conventional manner. The characteristic mark is completely inaccessible in the card. In the normal case, this indicator is not recognizable in the supervision, since the differences in thickness cannot be perceived in supervision alone. This makes it difficult to imitate this characteristic by corresponding deceptive color printing, as is attempted with conventional watermarks on paper, where, as is well known, a small color contrast can also be seen in the top view.

In Fig. 3, an advantageous embodiment of the principle explained is enlarged and shown schematically in section. To do this, the raster technique is used to build up the relief-like structure of the interface. In areas 4, which should appear darker when viewed, the height h4 of the individual point-shaped grid elements 7 is chosen to be greater than the height h6 of the grid elements in the main area of the map. In contrast, in adjacent areas 5 their height h5 is chosen to be smaller. The thickness of the opaque half part 3, averaged over the individual areas, is decisive for the light transmission, if the individual raster points are no longer or only poorly resolved visually. These averaged thicknesses are chosen so that the effect already explained with reference to FIGS. 1 and 2 can be seen in the review. Again, during embossing there is only a material shift from the light areas 5 to the dark areas 4. The design of the relief as a raster allows this material rearrangement in a simple manner and also increases the interface along which the two half parts are joined, so that the one-piece map composed of the two half parts is held together even better. The transparent half part 2 is in turn designed to be opposite.

The relief-like interface, which is created within the card 1 with the aid of the explained procedure, can also be connected to the see-through marking in the manner of the watermark in order to identify the card in supervision. One half is made of transparent, the other of opaque thermoplastic.

An embodiment which illustrates this is shown in FIGS. 4 and 5. FIG. 4 shows a relief structure of linear construction on the opaque half part 3, a configuration corresponding to FIG. 3 being recognizable in the central region. This structure is printed with a color strip 8, which runs in a straight line in vertical supervision. The opaque half part 3 designed in this way is combined with a transparent half part (not shown) of the same type to form a card, a section of which is shown schematically in FIG. 5. The review is shown in FIG. 5a. The straight line pattern 8 and the regions 4 and 5 forming the watermark can be seen. If the map is viewed from an oblique view, as shown in FIG. 5b, the line pattern 8 appears slightly wavy and the watermark disappears. Upon closer inspection in the oblique view, the watermark can still be recognized by the larger amplitude of the corrugation in the line pattern 8. The combination of transparency and supervision marking increases the difficulty of counterfeiting such cards and therefore further increases their security.

The described embodiments are designed in such a way that a watermark also appears when viewed, as explained above with reference to FIGS. 1 to 4. Further security features can also be provided therein.

It goes without saying that the flat surfaces of plastic types formed in this way can be printed in the known manner. For regulatory marking after

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the described. Art, windows should be provided in the appropriate places in the imprint. Furthermore, parts of the map information can also be present in the print pattern at the interface.

The arrangement described with a relief-like, optionally provided with a printed pattern, the interface between two card parts which are inseparably connected, results, as shown above, in manifold, advantageous ways of visually securing cards of this type, which were not previously available. Absolutely flat surfaces are preserved. Embossments in the card do not lead to a curvature, as was the case with the previously known composite cards. The security features are inaccessible to manipulation.

A particularly advantageous application of the see-through marking by means of the relief-like design of the interface of the opaque part 3 and the transparent part 2 according to FIGS. 1 to 3 is that the relief structure is formed in each case according to the portrait of the card owner from FIG. This portrait appears in watermark-like form when viewed and can be compared at any time with a photograph of the owner or himself. This enables an additional, individual identifier to be created. This is particularly possible because the relief-like structure of the interface can have continuously merging areas of different thicknesses, which - in contrast to conventional watermarks, which are usually designed in two stages - have an image with a continuous variation in brightness between a maximum and a minimum surrender.

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Claims (5)

650732 1. Card made of thermoplastic material with flat surfaces and visually perceptible, internal security signs, characterized in that the load-bearing part of the card consists of two half parts made of thermoplastic material of substantially the same thickness and flat outer surfaces, the first (2) of transparent , the second (3) made of thermoplastic material with an increased light absorption coefficient compared to the first half part and a positive or an opposite negative relief structure (4, 5, 6) is stamped into the inner surface of each half part, which has at least such height differences and dimensions in the Map level has that the differences in brightness produced in the view by the locally varying light absorption of the light passing through are perceptible to the eye, the two half parts with their embossed inner surfaces being laminated to one another to form a homogeneous piece. 2. Card according to claim 1, characterized in that the half-parts have non-embossed inner flat surface areas as a reference plane, against which the relief structure consists of raised and recessed zones, in such a way that in each case an elevated area laterally adjoins a recessed zone. 2nd PATENT CLAIMS 3. Card according to claim 1 and 2, characterized in that the relief-like structure has areas of different thickness, which merge into each other continuously. 4. Card according to one of claims 1 to 3, characterized in that at least a region of the relief-like structure of the inner interface has a grid-like shape (7). 5. The method for producing the planar card according to claim 2, wherein by means of an embossing mold on one side a relief in a first section of a transparent, thermoplastic plastic film and by means of a second, correspondingly oppositely designed embossing mold on one side an opposing relief in a second section of a thermoplastic plastic film the first increased light absorption coefficient is embossed, and that the two foil sections with the embossed surfaces are joined together inseparably, characterized in that raised and recessed areas adjoin one another in the embossing molds, in such a way that the embossing by shifting the plastic film mass from a recessed plane to an adjacent plane , areas higher than the zero level, the mean film thickness remaining unchanged due to the embossing.